The objectives of this project are: to validate the mircodialysis methodology and determine its sensitivity by recovering and measuring the levels of circulating nutrients (glucose and amino acids) from human dermis in vivo; to determine the influence of physiological aging on the delivery of nutrients to the skin. During Study 1 of this project, microdialysates will be collected from non-lesional and lesional skin of psoriatics together in the basal state together with samples from normal subjects who have undergone a dynamic glucose challenge or vasoactive manipulation (epinephrine or glucocorticoids). Rates of delivery of nutrients (glucose and/or amino acids) to the skin will be determined in basal states and following the dynamic tests. These experiments will determine the sensitivity of the methodology. During Study 2 of this project, microdialysates will be taken from subjects of two age ranges (20-50 yrs, n=5 and 50-70 yrs, n=5) in the basal state and after an appropriate challenge test as defined in Study 1. This study will measure local nutrients in the skin and define the functional impact of the known decline in the circulatory system with age.